Gary,
At least in Wisconsin, a mobile home is defined as follows; quoted in part from Section 66.0435
(d) ?Mobile home? is that which is, or was as originally
constructed, designed to be transported by any motor vehicle upon
a public highway and designed, equipped and used primarily for
sleeping, eating and living quarters, or is intended to be so used;
and includes any additions, attachments, annexes, foundations
and appurtenances.
There are distinctions made for "dependent" (not having complete bathroom facilities), and "nondependent" (those that do), but they have no bearing on whether it is considered a homestead. The only thing that matters is that it is your primary residence. Size also is not a consideration, but does factor into if or how it is taxed.
I have an umbrella policy, but as you wisely stated, individuals should check their respective state laws just to cover their assets.